Interesting...I've been reading lots of the links on the Why Boys Fail blog mentioned below. In one they discuss gross-out books as one way to get boys into reading, and the debate about whether this is the right tactic to use. There were other articles I read on similar subjects.
Why stands out for me is that two old-time remedies for boys' lack of interest in reading were never mentioned:
1) The comic book.
2) Science fiction.
The first is much more problematic than it used to be. Ever since the rise of the "Dark Knight" comic book in 1986 (I remember friends in college being so excited about that one!), comic books...sorry graphic novels aren't what they used to be. Now they are dark, moody, uber-violent and filled with se(x). I know there are still youth-oriented ones, but there aren't as many as there used to be, and as a parent, I would worry about boys wanting to move on to the more graphic of the graphic novels before they should.
The second seems like a good option. However, looking around the early reader section, I can think of only one sci-fi book that isn't a movie tie-in (6 year old boy loves "Wall-E".) Looking around the chapter book section, I'd have to say the same. Since J K Rowling, there has been a massive explosion of fantasy novels, but not sci-fi.
Some thing tells me there is a big market out there waiting to be tapped.